The present invention relates to a vehicle collision preventing apparatus by using a radar.
FIG. 1 is a block diagram of the conventional vehicle collision preventing apparatus.
In FIG. 1, the reference numeral (1) designates a radar for detecting the distance between the obstacle and the vehicle and relative velocity; (2) designates a danger determining circuit which determines the danger by the data of the radar (1). For example, it compares V.sup.2 (V: relative velocity) and 2.alpha.R (.alpha.: constant and R: relative distance). When V.sup.2 &gt;2.alpha.R, it determines to be danger whereby the danger signal output is generated. The reference numeral (3) designates a brake or an alarm device which actuates by the danger signal output of the danger determining circuit (2).
In the conventional apparatus, the signal reflected from the obstacle is remarkably varied depending upon the relative position between the obstacle and the radar (1). When the reflection signal reduces, the radar could not work for the detection of obstacle. The data from the radar (1) could not be given whereby the danger could not be determined and the danger signal output has not been given even though the dangerous obstacle is present.